载铂多级孔ZSM-5分子筛用于邻二甲苯的“吸附-催化燃烧”循环脱除

doi:10.15541/jim20180146

摘要/Abstract

摘要：

首先利用F127作为软模板, 采用蒸汽辅助晶化法合成出具有一定介孔结构的多级孔ZSM-5分子筛, 然后采用等体积浸渍法负载铂, 成功制备了载铂的多级孔ZSM-5分子筛催化剂。利用X射线衍射(XRD)、氮气吸附等温线(N₂ isotherm)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)对制备的催化剂进行了表征, 并将催化剂用于邻二甲苯的吸附和催化燃烧反应, 最后考察了催化剂“吸附-催化燃烧”循环脱除邻二甲苯的性能。结果表明, 与传统ZSM-5分子筛相比, 多级孔ZSM-5分子筛结晶度略有下降, 但是介孔度和孔体积明显提升。介孔结构与微孔结构并存, 极大提升了多级孔ZSM-5分子筛对邻二甲苯的吸附能力, 其饱和吸附量达到了传统ZSM-5分子筛的约8倍。此外, 介孔结构的存在提高了铂的分散度, 使得载铂多级孔ZSM-5分子筛具有最佳的催化燃烧邻二甲苯性能, 三次“吸附-催化燃烧”循环使用后的吸附容量依然基本保持不变, 并且在催化燃烧过程中无二次污染物生成, 具有较高的吸附容量和循环使用稳定性。

关键词: 负载铂催化剂, 多级孔分子筛, 挥发性有机物, 吸附, 催化燃烧

Abstract:

Pt/hierarchical ZSM-5 zeolites were successfully synthesized by the steam-assisted crystallization and subsequent wetness impregnation method. Structural features were characterized by XRD, N₂ isotherm, SEM, and TEM. Its catalytic behaviors for o-xylene storage at room temperature, and catalytic combustion of stored o-xylene at elevated temperatures were evaluated. It was found that crystallinity of the product underwent a reducing tendency after introduction of mesostructure, but the mesoporosity and pore volume were remarkably increased. Compared with Pt/conventional ZSM-5 zeolite, the o-xylene adsorption capacity of Pt/hierarchical HZSM-5 was around 8 times as that of the counterpart without mesostructure. Moreover, the Pt dispersion was improved due to mesoporosity. The highly dispersed Pt nanoparticles were beneficial for catalytic combustion of o-xylene. Futhermore, Pt/hierarchical ZSM-5 showed the efficient bi-functional performance during adsorption/catalytic combustion cycling process for o-xylene. Carbon balance was kept for three cycles without secondary pollutants, showing higher adsorption capacity and better reusing stability.

Key words: Pt-based catalysts, hierarchical zeolites, VOCs, adsorption, catalytic combustion

中图分类号:

TQ174

陈孟秋,王钰,杨登尧,邬红娟,郭利民. 载铂多级孔ZSM-5分子筛用于邻二甲苯的“吸附-催化燃烧”循环脱除[J]. 无机材料学报, 2019, 34(2): 173-178.

CHEN Meng-Qiu, WANG Yu, YANG Deng-Yao, WU Hong-Juan, GUO Li-Min. Pt Supported Hierarchical ZSM-5 Zeolite as Adsorbent/Catalytic Combustion Catalyst for o-xylene Elimination[J]. Journal of Inorganic Materials, 2019, 34(2): 173-178.

图/表 8

图1 Pt/mZSM-5、Pt/ZSM-5和Pt/mAl2O3催化剂的XRD图谱

Fig. 1 XRD patterns of Pt/mZSM-5, Pt/ZSM-5 and Pt/mAl2O3 catalysts

图2 Pt/mZSM-5, Pt/ZSM-5和Pt/mAl2O3催化剂的氮气吸附等温线(插图为孔径分布曲线)

Fig. 2 Nitrogen isotherms of Pt/mZSM-5, Pt/ZSM-5 and Pt/mAl2O3 catalysts with inset showing the corresponding pore size distribution curves

表1 催化剂的比表面积及孔结构参数

Table 1 Textural properties of the as-synthesized catalysts

Catalyst	S_BET^a/(m²•g^-1)	S_external^b/(m²•g^-1)	S_micro^c/(m²•g^-1)	V_micro^d/(cm³•g^-1)	V_pore^e/(cm³•g^-1)	D_pore^f/(nm•g^-1·cm³)
Pt/mZSM-5	383	254	129	0.07	1.19	19.7
Pt/ZSM-5	361	170	191	0.11	0.21	2.2
Pt/mAl₂O₃	191	189	2	/	0.50	8.5

图3 Pt/mZSM-5 (A, B), Pt/ZSM-5 (C)和Pt/mAl2O3 (D)催化剂的SEM照片

Fig. 3 SEM images of Pt/mZSM-5 (A, B), Pt/ZSM-5 (C) and Pt/mAl2O3 (D) catalysts

图4 Pt/mZSM-5 (A)、Pt/ZSM-5 (B)和Pt/mAl2O3 (C)催化剂的TEM照片

Fig. 4 TEM images of Pt/mZSM-5 (A), Pt/ZSM-5 (B) and Pt/mAl2O3 (C) catalysts

图5 Pt/mZSM-5、Pt/ZSM-5和Pt/mAl2O3催化剂的Pt 4f XPS谱图

Fig. 5 Pt 4f XPS spectra of Pt/mZSM-5, Pt/ZSM-5 and Pt/mAl2O3 catalysts

图6 (A) Pt/mZSM-5、Pt/ZSM-5和Pt/mAl2O3催化剂的邻二甲苯存储能力; (B) Pt/mZSM-5、Pt/ZSM-5和Pt/mAl2O3催化剂的邻二甲苯催化燃烧性能

Fig. 6 (A) Comparison of o-xylene adsorption capacity of Pt/mZSM-5, Pt/ZSM-5 and Pt/mAl2O3 catalysts; (B) Catalytic combustion of o-xylene to CO2 over Pt/mZSM-5, Pt/ZSM-5 and Pt/mAl2O3 catalysts

图7 Pt/mZSM-5催化剂上三次“吸附-催化燃烧”脱除邻二甲苯过程中, 二氧化碳和邻二甲苯浓度随时间变化曲线

Fig. 7 Concentration change of CO2 and o-xylene with time during three consecutive cycling process over Pt/mZSM-5 catalyst

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